Allocating internet protocol (ip) addresses to nodes in communications networks which use integrated is-is

ABSTRACT

Previously it has only been possible to allocate unique internet protocol (IP) addresses to nodes in open systems interconnection (OSI) communications networks such as those using integrated IS-IS, by manual configuration. This is time consuming and expensive because an operator must travel to the site of the node. By exploiting features of the OSI routing protocol the present invention enables IP addresses to be automatically allocated to the new network nodes. This is particularly advantageous for new intermediate systems such as optical multiplexers with integral routers. Once an IP address has been allocated, the node can be managed by a remote management system or operator using internet protocol methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/991,386, filed Nov. 13, 2001, entitled “ALLOCATING INTERNET PROTOCOL(IP) ADDRESSES TO NODES IN COMMUNICATIONS NETWORKS WHICH USE INTEGRATEDIS-IS”, the entirety of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a method of allocating internetprotocol (IP) addresses to nodes in communications networks which usethe integrated intermediate-system-to-intermediate-system (IntegratedIS-IS) routing protocol. The invention is particularly related to but inno way limited to optical communications networks, which comprise aplurality of directly connected routers or other intermediate systems.

BACKGROUND TO THE INVENTION

Intermediate-system-to-intermediate-system (IS-IS) protocol, also knownas Dual IS-IS, is a member of the open systems interconnection (OSI)suite of protocols and is a collection of extensions to the base IS-ISprotocol. Integrated IS-IS was developed to allow routers to supportboth IP and OSI traffic in parallel.

One feature of IS-IS and Integrated IS-IS routed networks is that theydo not require unique internet protocol addresses for each network node.Such OSI communications networks are increasingly integral with orconnected to internet protocol communications networks such as theinternet. However, because nodes in such OSI networks do not have IPaddresses it is not possible to use internet protocol type methods tocontact those nodes and carry out management or other tasks remotelyover the communications network.

For example, consider a node such as an optical multiplexer in anoptical communications network where the optical multiplexerincorporates a router and Integrated IS-IS routing protocol is used.When the new optical multiplexer and router are first installed in thecommunications network the router needs to be configured correctly inorder to operate as required in the particular network environment it isplaced in. (Also, if the OSI communications network is to route internetprotocol (IP) packets, the router typically needs one IP address foreach of its interfaces in order to function appropriately. At present,allocation of the required IP address is done by an operator who travelsto the router site, makes a physical connection directly to the routerusing a text terminal, and manually allocates appropriate IP addressesto the router interfaces. This is obviously time consuming andexpensive. It is not possible to remotely connect to the router over thenetwork using internet protocol means because the router interfaces haveno IP addresses by which they can be identified. This makes it very hardto remotely manage the router or other network node.

Known methods of automatically allocating IP addresses involve forexample Dynamic Host Configuration Protocol (DHCP) or Bootstrap Protocol(BOOTP). However, both these methods are applicable to TCP/IP networksand are not best suited to communications networks which comprise aplurality of directly connected routers or other intermediate systems.

Bootstrap Protocol is defined in the Internet Engineering Task Force's(IETF's) request for comments (RFC) number 951. It is a protocol whichenables a network user on a TCP/IP network to automatically receive anIP address and an operating system boot. A BOOTP server, managed by anetwork administrator, allocates the IP address automatically from alist of available addresses. However, the BOOTP method requires that fora new device to be added to a network and automatically assigned an IPaddress, it must be added so that it is directly connected to a BOOTPserver. This is problematic for complex networks such as those whichcomprise a plurality of directly connected routers or other intermediatesystems. In such cases, new network elements may need to be added sothat they are indirectly connected to the BOOTP server. However, this isnot possible without using a BOOTP relay server that is directlyconnected to the new network element. In order to provide an IP addressto such a new network element, the BOOTP relay server is used, inaddition to the BOOTP server itself. The BOOTP relay is connecteddirectly to the new network element. This is obviously complex andrequires BOOTP relay servers to be provided in addition to the BOOTPserver.

BOOTP is the basis for DHCP which is a more advanced network managementprotocol. DHCP can be used to automatically assign IP addresses to hosts(e.g. personal computers, print servers, terminals, etc.) on a TCP/IPnetwork. DHCP is described in IETF RFC 2131. However, DHCP suffers fromthe same drawbacks as BOOTP with respect to the need for new hosts to bedirectly connected to DHCP servers.

OBJECT TO THE INVENTION

An object of the present invention is to provide a method of allocatingIP addresses to nodes in a communications network which uses integratedIS-IS routing protocol such that the method overcomes or at leastmitigates one or more of the problems noted above. Further benefits andadvantages of the invention will become apparent from a consideration ofthe following detailed description given with reference to theaccompanying drawings, which specify and show preferred embodiments ofthe invention.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided amethod of automatically allocating a unique internet protocol (IP)address to a first node in an integratedintermediate-system-to-intermediate-system (IS-IS) communicationsnetwork said method comprising the steps of:

-   -   accessing information about one or more potentially available IP        addresses;    -   selecting one of the potentially available IP addresses; and    -   sending information about the selected IP address to nodes in        the communications network.

This provides the advantage that the first node is automaticallyassigned an IP address without the need for manual configuration whichis expensive and time consuming. For example, the first node may be anoptical multiplexer with integrated router, another type of intermediatesystem, or other suitable network node. The information can be sentusing a flooding method.

Preferably, said flooding method comprises the use of link state PDU(LSP) messages according to the integrated IS-IS protocol which isdescribed in IETF RFC 1195. This provides the advantage that a simpleway of informing network nodes of the new IP address is obtained that iseffective and easy to implement.

In another example, said flooding method comprises an adaptation of theconnectionless network service (CLNS) protocol. This is an alternativeto using the LSP messages. However, any other suitable type of floodingmethod can be used.

Preferably said step of accessing information comprises accessing aserver connected to the communications network. This provides theadvantage that by using a central server to manage allocation of IPaddresses, problems associated with duplication of IP addresses areavoided. Also, a central record of IP addresses is available to anadministrator or other management system.

Alternatively said step of accessing information comprises accessing thefirst node which has pre-specified information about one or morepotentially available IP addresses. This provides the advantage that noserver for IP address allocation is required. Instead, pre-specifiedinformation about potential IP addresses is stored on each node.

Advantageously, the method further comprises using said selected IPaddress to access the first node using an Internet Protocol managementsystem. This enables an administrator or management system to remotelyaccess the first node using internet protocol methods. For example, theadministrator could change the allocated IP address of the first node orcarry out other administration and configuration tasks.

According to another aspect of the present invention there is provided aserver connected to an integratedintermediate-system-to-intermediate-system (IS-IS) communicationsnetwork and arranged to automatically allocate an internet protocol (IP)address to a first node in that communications network, said servercomprising:

-   -   a store comprising information about one or more potentially        available internet protocol (IP) addresses;    -   a processor arranged to select one of the potentially available        IP addresses; and    -   an output arranged to issue one or more messages containing        information about the selected IP address.

This provides the advantage that a server can be used to automaticallyallocate IP addresses to nodes in an OSI communications network.

According to another aspect of the present invention there is provided acommunications network node for use in an integratedintermediate-system-to-intermediate-system communications network andrequiring a unique internet protocol (IP) address, said communicationsnetwork node comprising:

-   -   a store comprising information about one or more potentially        available internet protocol (IP) addresses;    -   a processor arranged to select one of the potentially available        IP addresses; and    -   an output arranged to issue one or more messages containing        information about the selected IP address.

According to another aspect of the present invention there is provided asignal comprising one or more integratedintermediate-system-to-intermediate-system routing protocol messages, atleast one of those messages comprising information about an internetprotocol address and an associated node.

The preferred features may be combined as appropriate, as would beapparent to a skilled person, and may be combined with any of theaspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to show how the invention may be carried into effect,embodiments of the invention are now described below by way of exampleonly and with reference to the accompanying figures in which:

FIG. 1 is a schematic diagram of an open systems interconnection (OSI)communications network according to the present invention;

FIG. 2 is a flow diagram of a method of automatically allocating an IPaddress to a node in an OSI network;

FIG. 3 is a flow diagram of another method of automatically allocatingan IP address to a node in an OSI network;

FIG. 4 is a table showing the seven OSI protocol layers according to theprior art.

FIG. 5 is a schematic diagram of a link state PDU and extension.

DETAILED DESCRIPTION OF INVENTION

Embodiments of the present invention are described below by way ofexample only. These examples represent the best ways of putting theinvention into practice that are currently known to the Applicantalthough they are not the only ways in which this could be achieved.

A communications network can be considered as a plurality of nodesinterconnected by links. Some of the nodes provide access points atwhich users (human or computer applications) can access thecommunications network. Such nodes providing access points are referredto as end systems (ES's) whilst nodes that are connected between suchES's are referred to as Intermediate Systems (ISs).

The present invention is concerned with packet based, connectionlesscommunications networks in which communications take place by sendingpackets (also known as protocol data units) containing user data andcontrol or signalling data between ES's via IS's. In order to effect thecommunication a particular method or set of rules is followed which isreferred to as a communications protocol. A communications protocol istypically formed from a plurality of sub-methods or protocol layerswhich can be considered as forming a protocol stack.

The Open System Interconnection (OSI) protocols are a suite of protocolsfor use in a communications network that is considered as comprisingseven layers as illustrated in FIG. 4. OSI defines one or more protocolsthat can be used for each of these seven layers to form a protocolstack.

The present invention is particularly concerned with intermediatesystems (IS's) which handle only protocol information at and below thenetwork layer (layer 3) whereas end systems (ES's) use protocols at allthe seven layers.

At the network layer, the OSI protocol suite specifies a routingprotocol, called intermediate-system-to-intermediate-system (IS-IS) aswell as an end-system-to-intermediate-system protocol (ES-IS). OSI alsoprovides specification about other features of the network layer. Theseinclude:

-   -   ISO (International Standardisation Organisation) 8648—which        defines the internal organisation of the network layer;    -   ISO 8348—which specifies network-layer addressing; and    -   ISO TR9575—which defines the framework, concepts and terminology        used in relation to OSI routing protocols.

In the case that OSI is used to provide a connectionless communicationsnetwork, further network layer protocols are used. These compriseConnectionless Network Protocol (CLNP) and Connectionless NetworkService (CLNS), as defined in the ISO 8473 standard.

As mentioned above, the OSI routing protocol IS-IS and its extension,integrated IS-IS, do not use unique IP addresses for each network node.Previously, in order to provide nodes in OSI networks with IP addressmanual configuration has been required. The present invention provides away of avoiding this in integrated IS-IS networks by allocating IPaddresses automatically.

Integrated IS-IS is defined in IETF RFC 1195 (December 1990) and asmentioned above it was developed to allow routers to support both IP andOSI traffic in parallel. The integrated IS-IS protocol is able tosupport pure-IP environments. Thus the present invention is applicableto all those types of environment in which it is required toautomatically allocate IP addresses to network nodes. For example,interconnection of dual (IP and OSI) routing domains with other dualdomains, with IP-only domains or with OSI-only domains is made possible.Although IETF RFC 1195 refers in detail to IP version 4 the inventiondescribed herein is equally applicable to IP version 6 and othersuitable IP versions.

Integrated IS-IS protocol comprises a method using so called LSP (linkstate PDU (protocol data unit)) messages. These are arranged to providea type of flooding mechanism. When an integrated IS-IS intermediatesystem receives an LSP, it makes a record of the information within thatLSP and then forwards the LSP on to all its neighbours. This method isused to enable each intermediate system to maintain a current picture ofnetwork topology. The present invention however, makes use of LSPmessages to perform the additional function of flooding informationabout new IP addresses.

Although Integrated IS-IS can route IP packets it does not use IPaddresses or IP packets in order to transmit topology information or toform adjacencies. This means that when a new network node is added to anIntegrated IS-IS network, that new node is able to operate immediatelywithout the need to be assigned an IP address. This differs from IPbased routing protocols such as open shortest path first (OSPF) wherenew routers require an IP address in order to form adjacencies, transmittopology information and start routing. Also, each network node in anIntegrated IS-IS or IS-IS network has a unique system identifier (SID).These SIDs may be derived from a unique MAC (media access control)address that is allocated to the node during the manufacturing process.

FIG. 2 is a flow diagram of a method by which LSP messages are used inconjunction with a central server, to automatically allocate an IPaddress to a new network node in an integrated IS-IS communicationsnetwork. The new network node is preferably an intermediate system butmay be any type of network node.

In this method, a central server is provided connected to the OSIcommunications network. The central server comprises a store or databasecontaining information about existing network nodes and theircorresponding IP addresses. In addition the central server hasinformation about one or more IP addresses which are available for usein the communications network.

When a new network node, which has no IP address, is added to thecommunications network (see box 20 of FIG. 2) it sends a message to thecentral server to request an IP address. This can be achieved in anysuitable manner. For example, the new network node may have access topre-specified information about the location of the central server.Alternatively, the new network node may receive LSP extensions whichprovide the address of the central server. Another possibility is thatthe new node simply broadcasts a request and this eventually reaches thecentral server. By any such suitable means, the central server becomesaware of the new network node (box 21 in FIG. 2). The central serverthen takes one of the IP addresses which it has available for use andinforms the new network node, and other nodes in the network about thisusing the LSP mechanism. That is, the central server issues one or moreLSPs with extensions containing information about the new IP address andassociated node (see box 22 of FIG. 2). The LSPs and extensions areforwarded through the network as described above and eventually the newnetwork node receives one and obtains its IP address.

FIG. 5 is a schematic diagram of an LSP control or signalling message 52comprising an LSP 50 and an LSP extension 51. The IP address is added tothe LSP extension and intermediate system nodes are arranged torecognise such LSP extensions.

Advantageously, any nodes which do not understand or recognise LSPextensions simply ignore the extension and deal with the LSP part of themessage as normal. This is advantageous because it is not necessary toenable all network nodes to understand or recognise the LSP extensionswhilst still enabling the IP address information to spread through thenetwork.

A network administrator is then able to connect to the communicationsnetwork and obtain information about the new node's IP address eitherfrom the central server of from any node which maintains topologyinformation. Using that IP address the network administrator is able touse internet protocol methods to contact and manage the new network noderemotely over the communications network. For example, the networkadministrator could change the allocated IP address to another IPaddress or perform other configuration actions (see box 23 of FIG. 2).

By using a central server in this way it is easy to ensure that all thenetwork nodes have unique IP addresses and problems with duplicate IPaddresses are avoided.

In another embodiment, no central server is required. Instead a new nodeis able to select its own IP address from a plurality of pre-specifiedIP addresses. This is now described with reference to FIG. 3. LSPmessages are again used but this time LSP extensions 51 are notrequired; instead the IP address information is carried in the LSP 50itself. An advantage of this is that no TLV needs to be requested fromthe IETF or ISO as described below. As before, the new node ispreferably an intermediate system but this is not essential.

In this example, each new network node has one or more pre-specified IPaddresses (see box 30 of FIG. 3). For example, these may be allocated tothe network node during the manufacturing process. When the new networknode is added to the communications network it waits for a specifiedduration and receives LSPs from other network nodes during that time.The new network node examines those LSPs (see box 31) which containtopology information and information about the IP addresses of othernodes in the communications network. For example, FIG. 5 has a schematicdiagram of a LSP 50 which comprises a fixed part 54 and a variable part53. The fixed part contains a field (LSPID) which contains the addressof the node which created the LSP and this address can be an IP address.The variable part 53 contains addresses of any IS neighbours of the nodewhich created the LSP and also addresses of any ES neighbours of thatnode.

Once the specified duration is over, the new network node allocatesitself an IP address by selecting one IP address from thosepre-specified IP addresses associated with it. This selection is made onthe basis of the information received in LSPs (see box 32 of FIG. 3).For example, those LSPs may contain information about two other IPaddresses. The new network node then assumes that those two IP addressesare in use and does not select them.

The new network node now has an IP address and the network administratoror management system is able to contact the new node using its IPaddress as in box 23 of FIG. 2 and box 34 of FIG. 3. The new networknode generates its own LSPs containing its chosen IP address andforwards those to other nodes in the network.

In the case that two new network nodes are added to the networksimultaneously, there is a possibility that these two nodes will beallocated the same IP address. To avoid this, the new network nodescontinue to check all LSPs they receive for IP addresses. If the IPaddress in a received LSP message is the same as the network node's ownIP address, then that network node selects a different IP address fromthe pre-specified addresses available to it (see box 32 of FIG. 3). Inthis way, the problem of duplicate IP addresses being used is reducedwithout the need for a central server to be provided.

In another embodiment, the CLNS protocol is made use of as opposed tothe LSP method of Integrated IS-IS protocol. A flooding type method iscreated for use in CLNS similar or equivalent to the LSP method ofintegrated IS-IS. This is then used to broadcast the information aboutthe new node's IP address. Either of the methods of FIGS. 2 and 3 can beused but replacing the LSP method by a CLNS flooding method and ensuringthat the network nodes are able to understand CLNS in order to obtainthe IP address information from the CLNS messages. This provides theadvantage that no information needs to be added to LSP messages ofintegrated IS-IS. In order to add such information a TLV (type lengthvalue) needs to be requested from the IETF or ISO and so by adaptingCLNS instead this need is avoided. Any suitable flooding method can beprovided within the CLNS protocol.

In another embodiment, a central address server is used as in the methodof FIG. 2, but without the need to use LSP extensions. This has theadvantage that no TLV number needs to be requested from the IETF or ISO.In this embodiment, the IP address for the new node is carried in theLSP 50 itself, for example in the LSPID field, the IS neighbours fieldor the ES neighbours field (see FIG. 5). In order to explain thisembodiment, some background information about LSPs and their useaccording to the prior art is now given.

Routers in an integrated IS-IS network each maintain a link statedatabase which contains a record of the most recent LSP received fromvarious other routers in the network. Each LSP has a sequence number(see FIG. 5) to distinguish between LSPs created by the same node. Forexample, if the first LSP created by a node has sequence number 1 thenthe second LSP created by that node has sequence number 2. When a routerreceives an LSP it decides whether to update its link state databasewith the received LSP. For example, if the received LSP is older than acorresponding LSP in the database (as determined by the sequence numberand LSPID) then it is simply forwarded on with no database update beingdone. If the received LSP is more recent than any corresponding LSP inthe database, then the received LSP is used to overwrite thatcorresponding LSP in the database. The received LSP is also forwarded onto all the node's neighbours.

The present invention makes use of this behaviour with respect tosequence numbers in order to pass on IP address to a new node. Themethod is the same as that described in FIG. 2, except for the manner inwhich box 22 is implemented. The central server generates an LSP whichhas an anomalous sequence number and which contains the IP address forthe new node, stored in the LSP itself, for example in the LSPID field,ES neighbours field, IS neighbours field or any other suitable field.The new node is arranged to retain any LSPs it receives with anomaloussequence numbers and to determine its IP address by accessing apre-specified field of such LSPs. Any suitable anomalous sequence numbermay be used such as one which is more than a specified number of unitshigher than current average sequence numbers.

In the example of FIG. 2 the central address server becomes aware that anew network node has been added to the network (box 21 of FIG. 2) and asexplained above this is achieved in any suitable manner. For example,the new network node can indicate to the server that it needs an IPaddress by for example:

-   -   issuing LSPs that indicate that the new node supports IP but        which do not provide an IP address;    -   issuing LSPs that contain an anomalous IP address such as one        with a sub-net mask of all zeros;    -   issuing LSPs that contain a pre-specified IP address;    -   issuing LSPs that contain anomalous, “fake”, or pre-specified        adjacency information.

These methods can also of course be used by a server which wishes toadvertise the fact that it is capable of assigning IP addresses.

In a preferred example, the new network node issues LSPs that contain ananomalous IP address. The server receives these LSPs and realises thatthe originating node requires an IP address. The server then overwritesthe anomalous IP address with an IP address suitable for the new node,increases the LSP's sequence number, and forwards that LSP back to theoriginating node. The originating node realises that the sequence numberis too high and so realises that the LSP contains an IP address foritself. (Please add more detail here if necessary. For example, where isthe IP address stored in the LSP?)

FIG. 1 is a schematic diagram of an open systems interconnection (OSI)communications network according to the present invention. One or moreintermediate systems, such as routers 11 to 15, are connected togetherwithin the network, which also comprises end-systems and user terminalsalthough these are not shown for clarity. In the embodiment of FIG. 2 aserver 10 is used as illustrated in FIG. 1 although this is notessential. The OSI network 19 is connected via a gateway node 16 to aninternet protocol communications network 18 such as the Internet. Usingthe methods of the present invention, one or more of the routers 11 to15 are each automatically allocated an IP address. This may be anysuitable type of IP address such as IP version 4 or IP version 6. Once arouter is allocated an IP address, a human operator or automatedmanagement system is able to remotely manage that router for example,using a user terminal 17 connected to the IP network 18 or a managementsystem 9.

A range of applications are within the scope of the invention. Theseinclude situations in which it is required to allocate IP addressesautomatically to nodes in an OSI communications network, such as anintegrated IS-IS network.

1. A method of automatically allocating an internet protocol (IP)address in a communications network, the method comprising: maintaininginformation about a plurality of available IP addresses; allocating oneof the plurality of available IP addresses to a node of thecommunications network, the allocated one of the plurality of availableIP addresses being a unique IP address to be used for accessing the nodeof the communications network; informing the node of the communicationsnetwork of the unique IP address; and accessing, by an IP managementsystem, the node of the communications network using the unique IPaddress.
 2. The method of claim 1, wherein informing the node of thecommunications network of the unique IP address comprises sendinginformation about the unique IP address to the node in link stateprotocol data units.
 3. The method of claim 2, wherein sendinginformation about the unique IP address to the node in link stateprotocol data units comprises sending the information in link stateprotocol data unit extensions.
 4. The method of claim 2, wherein sendinginformation about the unique IP address to the node in link stateprotocol data units comprises sending the information in link stateprotocol data units with anomalous sequence numbers.
 5. The method ofclaim 1, wherein the node of the communications network has no assignedIP address until the node is informed of the unique IP address allocatedto the node.
 6. The method of claim 1, comprising determining that thenode has been logically added to the communications network when thenode has been informed of the unique IP address allocated to the node.7. The method of claim 1, wherein maintaining the information about theplurality of available IP addresses comprises maintaining theinformation about the plurality of available IP addresses at a serverconnected to the communications network.
 8. The method of claim 1,wherein maintaining the information about the plurality of available IPaddresses comprises maintaining the information about the plurality ofavailable IP addresses at the node the communications network.
 9. Themethod of claim 1, comprising changing the IP address allocated to thenode of the communications network using the IP management system. 10.The method of claim 1, wherein the communications network is an opensystems interconnection (OSI) communications network.
 11. The method ofclaim 10, wherein the OSI network is an integratedintermediate-system-to-intermediate-system (IS-IS) communicationsnetwork.
 12. The method of claim 10, wherein the integrated IS-IScommunications network is configured to use IS-IS routing protocol. 13.The method of claim 1, wherein the node of the communications networkcomprises an intermediate system.
 14. The method of claim 1, wherein thenode of the communications network comprises a router.
 15. The method ofclaim 1, wherein the node of the communications network comprises anoptical multiplexer with an integral router.